Renal ammonia formation is impaired in diseases of the kidney such as chronic renal failure and in other pathologic conditions such as starvation, uncontrolled diabetes mellitus or adrenal insufficiency. These diseases can lead to potentially life threatening metabolic acidosis due to the inability to excrete acid as NH4+. The source of urinary NH3 is the amino acid glutamine. The deamidation of glutamine yields NH3 and glutamate, and the metobolism of the resulting glutamate probably regulates ammoniagenesis in kidney. Two biochemical pathways deaminate glutamate in kidney, namely, glutamate dehydrogenase (GDH) and the purine nucleotide cycle (PNC). Evidence is provided that both pathways can form significant and approximately equal amounts of NH3 from glutamate in kidney. The P.I. proposes the PNC deaminates glutamate present in tissue cytosol during the earliest phases of acidosis in the rat. During chronic acidosis in rat NH3 formation is via GDH. The P.I. proposes the PNC may form large quantities of NH3 during acute and chronic acidosis in the dog. The difference is due to PEPCK activity in the 2 species. In rat PEPCK adapts to decrease oxalacetate levels which inhibits transamination and thereby promotes glutamate deaminaction via GDH. In the dog PEPCK activity does not increase, oxalacetate levels are elevated and transamination may be favored for glutamate deamination via the PNC. The P.I. also proposes the rate of ATP turnover in kidney may regulate glutamate deamination via both the PNC and GDH. It is possible NH3 formation may be linked to the process of urinary acidfication via the cells' metabolic needs for energy. The aim of the proposed research is to accurately determine the relative contribution of both pathways to NH3 formation by using amino-[15N] glutamine in preparations of dog and rat kidney. The incorporation rate of [15N] into the 6-amino group of adenine nucleotides will precisely define the contribution of the PNC (versus GDH) to ammoniagenesis during altered physiological states. Cellular energy metabolism will be examined by saturation transfer techniques of whole tissue in NMR and by measurement of the adenine nucleotide translocase in mitochondria. The results of this study may provide useful information on the regulation of NH3 formation in kidney.